1. Field of the Invention
The present invention is related to apparatus and method for the continuous treatment of surfaces of articles of reduced thickness, for example for the treatment of fragile products of small dimensions.
2. Discussion of Background Information
The apparatus and method to which the present invention relate can be advantageously applied to the implementation of diverse operations for the treatment of surfaces of small articles, a non-exhaustive list of which follows:
cold or hot coating, with a liquid and/or powdery admixture, of products such as candy and other confectionery goods, cookies, peanuts, dry fruits, grains, flakes of cereals, gelatinized products, extruded products, etc.;
"frosting" candy and other confectionery products (striping of products coated with sugar-based solution, to stop them from amalgamating together);
"oiling" of peanuts and gelatinized products (application of a thin layer of an oily admixture, to obtain a finished appearance);
"gumming" (depositing a thin layer of gum adapted to retain a powdery product around a solid or compact core, for example to retain salt on certain products, sugar on fruit jellies, dates, etc.; or to maintain the density of brittle products, for example, by depositing a thin layer of gum around a core constituted by a main active agent of pharmaceutical tablets);
hot or cold mixing of products, for example mixtures of dry fruits, grated vegetables, etc.;
applying or removing films from seeds, grains, peanuts, etc.;
"loosening" of products (for example, separation of jellied fruits or other agglutinated products);
sifting and sizing;
brushing or glazing.
The EP-A-0,192,102 discloses an apparatus for uniformly and continuously coating confectionery goods comprising a solid, or gelatinous, or sticky core, coated in liquid and/or powdery products, of the type comprising a substantially horizontal fixed chute, an endless screw which is driven rotationally in the chute, and means to introduce the cores and the liquid and/or powdery products into the chute. The apparatus also comprises at least one helical brush that are formed of bristles implanted radially in a helix on one or two drive shafts that are rotationally driven in the chute at a speed less than 100 revolutions/minute. The chute has the shape of a trough which is opened towards the top, having a height greater than the diameter of the brushes and having a cylindrical base that envelopes the brushes in the portion located beneath the drive shafts.
The performance of such a machine is mediocre. Indeed, the products are pushed in a single direction by the helical brush, and if the products do not have a rounded shape (tablets, round sections of french fries, etc.), these products slide on the wall of the chute instead of turning about themselves, thereby resulting in:
unsatisfactory coating of the products if the machine is used for this function;
inadequate separation of the product units, leading to a choking effect and then a blocking effect that blocks the machine, when the machine is operated in order to implement the "frosting" operation;
a mediocre brushing of the products if the machine is used for this end. To obtain a satisfactory result the chute as well as the helical brush must be extended, and the passage time of the products in the chute must be increased.
On the other hand, when this machine is used to treat viscous, sticky or gluey products, or another product, with a liquid or powdery admixture, the core of the brushes quickly gets excessively encrusted, without any possibility of cleaning these brushes during the functioning of the machine.
FR-A-2,596,956 discloses a machine for the manufacture of coated products, comprising:
a cylinder turning about a substantially horizontal axis whose downstream end is open;
a helical brush with flexible bristles located inside the cylinder, at the upstream end of the cylinder, and which is rotationally affixed to the cylinder;
and a conveyor belt composed of a second helical brush with flexible bristles, which is driven in rotation inside a fixed tube is coaxial with respect to the rotary cylinder which penetrates slightly inside the upstream end of the latter.
The first important disadvantage of this machine is the fact that the rotary cylinder and the helical brush mounted in a fixed manner inside the cylinder turn simultaneously, and in the same direction in such a way that the units or particles of the products are not brushed and agitated from all directions, but are pushed in the direction of the exit by sliding on the internal wall of the cylinder, and this results not only in mediocre agitation and coating, but also in a mass effect due to the accumulation of products which, when they are fragile (pieces of french fries or others), can break and disintegrate. This detrimental phenomenon is accentuated by the presence, inside the cylinder, of radial spacers that rigidly link the cylinder and the axial shaft of the helical brush.
Moreover, the cleaning of such a machine, whose internal surfaces are rapidly covered with deposits resulting from the use of viscous or syrupy products, is very difficult to implement.